1. Field of Invention
The invention relates to a recordable optical recording medium and the reading mechanism thereof. In particular, the invention relates to a recordable optical recording medium containing preinstalled information, the method of reading the preinstalled information, and the circuit thereof.
2. Related Art
In order for an optical disc drive to identify the address and parameters of a blank recordable optical disc, the optical disc manufacturer has to preinstall some information on the blank disc. Such information includes the manufacturer identification (ID) code, a recommended optical writing power, initial and terminal addresses of the recordable region, and actual addresses of various important sectors. If the information is preinstalled (or pre-recorded) on the land of data tracks, a simple circuit can be used directly detect the data. However, such data occupy certain recordable space. Therefore, a common solution is to preinstall the information in the servo signal. However, this requires one to add a corresponding detection circuit in the servo channel. The latency of decoding is not good for rapid random access.
Take the information preinstallation of a CD-R/RW disc as an example. The information is recorded in the wobble groove by frequency modulation (FM). The wobble is a sine wave of 23.05 KHz or 21.05 KHz. The 23.05 KHz high frequency means “1” while the 21.05 KHz low frequency means “0.” At standard rotation speeds, the carried information is 42 bit*75 Hz. The detection method requires the use of a bipolar phase-lock circuit.
The DVD+RW disc adopts another mechanism to preinstall information. The information is stored in the wobble groove by phase modulation (PM). The wobble is an 817.5 KHz monotonic sine wave. The cycle with an initial phase equal to 0 degree means “0.” The cycle with an initial phase equal to 180 degrees means “1.” The detection of the preinstalled information requires the use of high-speed analog-to-digital (A/D) integrated circuit (IC) chip and a phase-lock circuit.
The pregroove of the DVD-R/RW disc also has wiggles, which is a 140.6 KHz sine wave. However, this wobble groove is used to record the preinstalled information, but only for rotation speed control. The actual recording location of the preinstalled information is in the so-called “prepit.” Its detection only requires a comparator and a filter. The above-mentioned three types of preinstalled information and their reading mechanisms are hidden in the servo signal. For the DVD disc, the preinstalled information is etched in the read-only region in the beginning of each sector. The disc drive can directly detect such information from the data signal. However, how to reduce the complexity of reaching circuit and to make it suitable for rapid random access is still an important direction in the development of preinstalled information mechanisms for optical discs.